1. Field of the Invention
The invention relates in general to a printer, and more particularly to a printer with print head cleaning function.
2. Description of the Related Art
Referring to both FIG. 1A and FIG. 1B. FIG. 1A illustrates a side view of a cartridge and a document feeder of a printer, while FIG. 1B illustrates a partly enlarged diagram of FIG. 1A. The printer 100 includes a housing 101, a shaft 103, a carrier 105 and a document feeder. The carrier 105 is disposed on the shaft 103. The carrier 105 reciprocates along the shaft 103. The document feeder includes a roller 102a and a roller 102b. When the printing paper 140 is sent to the position shown in the diagram through the document feeder, the roller 102a and the roller 102b, the print head 110 of the cartridge 109 has a pen-to-paper space (PPS) with respect to the paper 140. If the PPS is not a fixed value, then the ink of the print head 110 will not be uniformly spread over the paper 140. Therefore, a constant PPS is crucial to assuring the printing quality of the printer 100. However, the thickness of the printing paper is not always the same. For example, the Plain Paper typically has a thickness of 0.12 mm, while the Photo Paper typically has a thickness of 0.25 mm. In order to maintain a constant PPS so that the printing quality of the printer 100 can be assured, the cartridge 109 has to be adjusted according to the thickness of the printing paper.
A printer adopting an eccentric shaft is disclosed in Japan Patent Publication No. JP2001-047688. The print head is adjusted according to the thickness of the printing paper. By rotating the eccentric shaft to the corresponding position, the carrier moves upward or downward correspondingly for the PPS to be maintained fixed so that the printing quality of the printer is assured. However, it is difficult and costive to control the eccentric distance precisely.
Referring to FIG. 1A and FIG. 1B again. If only the height of the carrier 105 and the height of the cartridge 109 are raised up, a number of problems would occur. For example, the print head 110 of the cartridge 109 needs to be cleaned after a period of service. If the height of the cleaner (not shown in the diagram) used for cleaning the print head 110 is not raised up, the print head 110 would not be cleaned thoroughly. The reason is that an optimum interference distance exists between the print head 110 and the cleaner, and the cleaning quality will be affected if the distance between the print head 110 and the cleaner is larger or smaller than the interference distance. Currently, examples of resolving the change in the interference distance include United State Patent Publication No. US20030122892, which maintains a fixed interference distance between the cleaner and the print head by a device such as a relay for instance. Such practice is an electronic control, and would further increase the cost.